1. Field of the Invention
The present invention relates to mechanical seals, and more particularly having an improved mechanical seal having an elastic element and a mechanical seal having an improved means to secure the seal to a machine stationary housing.
2. Description of the Related Art
A mechanical seal provides a seal between a rotatable element, typically a shaft, and a stationary housing of an apparatus, typically containing fluid. Such seals are often associated with a fluid pump having a shaft extending through a pump housing wall. The pump shaft can be coupled to a motor through a motor shaft. The mechanical seal forms a seal between the pump shaft and the outer surface of the pump housing. Mechanical seals for such applications are commercially available and are described in U.S. Pat. Nos. 4,639,000; 4,832,351, 4,989,882; and 4,993,720. Such seals endure rigorous environments and last for extended time periods.
Seals which are known in the art comprise rotatable components and stationary components which contact to form a seal at opposing sealing surfaces. The rotatable components include a shaft attachment means. Such a means is typically a sleeve having an inner perimeter surface which sealingly fits over the outer perimeter surface of the shaft and is connected to the shaft by connecting means such as set screws. An "O" ring typically provides a seal between the shaft and the sleeve. There is a rotatable circumferential seal element interconnected to the sleeve so as to rotate when the shaft and sleeve rotate. The sleeve extends axially along the shaft.
The stationary components comprise a gland which extends circumferentially around the shaft. The gland abuts against the outer housing surface around the shaft. There is typically a sealing gasket interconnected to the gland and located between the gland and the housing. The gland functions as a base by which the seal is attached to the housing. The connection is typically accomplished by bolts extending from the outer housing wall. The bolts pass through slots or connecting extensions extending radially from the gland through the connecting slots or connecting extensions and secured with nuts. A stationary seal element is located between the inner circumferential surface of the gland facing the shaft (i.e. the gland inner surface) and the shaft. The stationary seal is directly or indirectly connected to the stationary gland. There are suitable means such as described in U.S. Pat. Nos. 4,832,351 and 4,989,882 to axially center the various stationary elements on the shaft. A circumferential spacing is maintained between the stationary elements, and the shaft and various of the rotating elements.
The stationary and rotatable components meet at opposing sealing surfaces of the rotatable and stationary seal elements. There is typically a metal spring which forces either one of the seal elements toward the opposing seal element to cause the opposing surfaces to be pressed together. The opposing seal element has restricted axial movement and the surface of one seal element is forced by the spring against the surface of the opposing seal element. Thereby, a seal is formed between the opposing sealing surfaces, i.e., the rotatable and stationary sealing elements.
Mechanical seals known in the art have at least one "O" ring associated with the sealing element being acted on, by the spring. The spring forces this element toward the opposing element to form a seal. The "O" ring must form a seal not withstanding the axial movement and is known as a "dynamic" "O" ring. Additionally, the dynamic "O" ring is located in an "O" ring slot which can clog. The spring must therefore provide force to cause the sealing elements to come together under sufficient pressure to form a seal while overcoming the resistance of the dynamic "O" ring and clogging in the area of the dynamic "O" ring. It would be desirable to eliminate the dynamic "O" ring as well as the metal spring.
Additionally, the means to connect the mechanical seal to the housing is integrated into the structure of the stationary components. The mechanical seal is often set in place and removed in the small space between the pump and motor. The means to attach the seal take up space and make access to the mechanical seal difficult for both installation and removal. A design with easier access to the seal elements at the location where the shaft extends from the housing is desireable.